An internal combustion engine often includes an engine starter motor for rotating the engine from a stopped state to a cranking speed. The starter may engage the engine during engine starting and it may be disengaged from the engine after the engine starts and is rotating under its own power. The engine starter may engage the engine while the engine is approaching zero speed to decrease engine starting time for vehicles that have engines that may be automatically stopped and started (e.g., stop/start vehicles). In addition, the starter may reengage the engine at higher speeds if there is an indication that the engine should continue to operate after an engine stopping procedure has begun. In other examples, the starter may be in the form of an integrated starter/generator or a belt driven starter/generator. Integrated starter/generators and belt driven starter/generators may be coupled to the engine so that engaging the engine is not necessary. Nevertheless, whether the engine starter is a conventional starter that selectively engages and disengages from the engine or a form of integrated starter/generator, the starter may be used at a much higher frequency in a stop/start vehicle than in vehicles with engines that remain running except when stopped by the vehicle's human driver. Starters that are used more frequently may be constructed more robustly to meet life cycle requirements. However, increasing robustness of a starter to meet a desired starter life cycle may increase system cost. Therefore, it may be desirable to provide an engine starting system that meets a desired life cycle at a desirable cost.
The inventors herein have recognized the above-mentioned issues and have developed a vehicle operating method, comprising: estimating an amount of engine starter useful life consumed via a controller; adjusting automatic engine stop/start thresholds in response to the amount of engine starter useful life consumed; and starting or stopping the engine in response to the automatic engine start/stop thresholds via the controller.
By adjusting automatic engine stopping and starting thresholds in response to an amount of engine starter useful life consumed, it may be possible to decrease frequency and rigorousness of automatic engine stops and starts so that an engine starter may operate over its expected life cycle without grossly increasing system cost. In addition, automatic engine stopping and starting may still be permitted with the engine starter so that the vehicle's fuel efficiency may be relatively high. In some examples, if the percent of useful life consumed of the engine starter is less than a threshold, the automatic engine stopping and starting thresholds may be returned to base values. In this way, automatic engine stopping and stopping entry conditions may be made more or less rigorous depending on how the engine has been previously stopped and started so that engine starter life may meet expectations while delivering desirable fuel economy.
The present description may provide several advantages. For example, the approach may allow an engine starter to reach a desired life span. In addition, the approach may allow engine starter life spans to be met without having to make the engine starter suitable for extreme duty cycle conditions. Also, the approach adjusts for severity of engine starter use to increase engine starter life and providing desirable fuel economy.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.